Wikipedia
Apokolips is a fictional planet appearing in American comic books published by DC Comics. The planet is ruled by Darkseid, established in Jack Kirby's Fourth World comic book series, and is integral to many stories in the DC Universe. Apokolips is considered to be the opposite of the planet New Genesis.
Apokolips is a large planet and an ecumenopolis with burning fire pits. The war that destroyed the Old Gods and created New Genesis and Apokolips separated the Fourth World from the rest of the universe, leaving it only accessible by a form of travel called a boom tube.
The Boom Tube, it has been revealed, converts individuals that pass through to proportions fitting the destination, i.e., when a New God passes from Apokolips (or New Genesis) to Earth, they are shrunken in size, while someone going the other way would grow larger. If someone somehow reaches the Fourth World by other means, he will discover its denizens are giants.